+static int push_metadata(struct lttng_consumer_channel *metadata,
+ const char *metadata_str, uint64_t target_offset, uint64_t len)
+{
+ int ret;
+
+ assert(metadata);
+ assert(metadata_str);
+
+ DBG("UST consumer writing metadata to channel %s", metadata->name);
+
+ assert(target_offset == metadata->contig_metadata_written);
+ ret = ustctl_write_metadata_to_channel(metadata->uchan, metadata_str, len);
+ if (ret < 0) {
+ ERR("ustctl write metadata fail with ret %d, len %ld", ret, len);
+ goto error;
+ }
+ metadata->contig_metadata_written += len;
+
+ ustctl_flush_buffer(metadata->metadata_stream->ustream, 1);
+
+error:
+ return ret;
+}
+
+/*
+ * Flush channel's streams using the given key to retrieve the channel.
+ *
+ * Return 0 on success else an LTTng error code.
+ */
+static int flush_channel(uint64_t chan_key)
+{
+ int ret = 0;
+ struct lttng_consumer_channel *channel;
+ struct lttng_consumer_stream *stream;
+ struct lttng_ht *ht;
+ struct lttng_ht_iter iter;
+
+ DBG("UST consumer flush channel key %lu", chan_key);
+
+ channel = consumer_find_channel(chan_key);
+ if (!channel) {
+ ERR("UST consumer flush channel %lu not found", chan_key);
+ ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+ goto error;
+ }
+
+ ht = consumer_data.stream_per_chan_id_ht;
+
+ /* For each stream of the channel id, flush it. */
+ rcu_read_lock();
+ cds_lfht_for_each_entry_duplicate(ht->ht,
+ ht->hash_fct(&channel->key, lttng_ht_seed), ht->match_fct,
+ &channel->key, &iter.iter, stream, node_channel_id.node) {
+ ustctl_flush_buffer(stream->ustream, 1);
+ }
+ rcu_read_unlock();
+
+error:
+ return ret;
+}
+
+/*
+ * Close metadata stream wakeup_fd using the given key to retrieve the channel.
+ *
+ * Return 0 on success else an LTTng error code.
+ */
+static int close_metadata(uint64_t chan_key)
+{
+ int ret;
+ struct lttng_consumer_channel *channel;
+
+ DBG("UST consumer close metadata key %lu", chan_key);
+
+ channel = consumer_find_channel(chan_key);
+ if (!channel) {
+ ERR("UST consumer close metadata %lu not found", chan_key);
+ ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+ goto error;
+ }
+
+ ret = ustctl_stream_close_wakeup_fd(channel->metadata_stream->ustream);
+ if (ret < 0) {
+ ERR("UST consumer unable to close fd of metadata (ret: %d)", ret);
+ ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
+ goto error;
+ }
+
+error:
+ return ret;
+}
+
+/*
+ * RCU read side lock MUST be acquired before calling this function.
+ *
+ * Return 0 on success else an LTTng error code.
+ */
+static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)